Equipment for telecommunication installed in rooms, during operation generates a considerable amount of heat energy. This occurs continuously and the temperatures around the equipment have to be maintained within certain limits. Particularly important is that a specified maximum temperature must not be exceeded. In order to achieve this temperature regulation, usually mechanical cooling systems e.g. compressor operated evaporation systems are used. In those the warm indoor air passes an evaporator and is cooled. Thereafter the cooled air is recirculated to the room. The continous heat generation requires continuous cooling.
In case of failure of e.g. a compressor cooling system some kind of reserve system has to be activated and provide cooling of the indoor air. One method to obtain reserve cooling is to provide cool liquid in a tank. At failure of the compressor cooling system, cold liquid is pumped from said tank to an air cooler in which the indoor air is cooled and is then pumped back to the tank again. This system however, can operate only a limited time since the liquid in the tank gradually becomes warmer. Therefore a system for obtaining reserve time for cooling indoor air is discussed.